This invention relates to pigmented coating compositions, notably paints, which are based on polymers curable by an autoxidative process under the influence of visible or ultra-violet light.
It is well-known that certain polymers, in particular oil-modified alkyd resins, have the property of curing, i.e. crosslinking, in the presence of oxygen by an autoxidative polymerisation process. In the formulation of useful air-drying paint compositions incorporating such resins, it is common practice to include catalytic compounds which accelerate the autoxidation process, for example, metallic driers such as cobalt naphthenate or lead naphthenate. In the absence of such catalysts, the curing of the resin is normally a very slow process of no commercial significance.
However, the use of metallic driers may be undesirable in certain circumstances since, for example, they provide an unsatisfactory rate of drying at low ambient temperatures; they encourage the formation of a skin in a partially filled can of paint; and metals such as lead are toxic.